Processed polypeptides with IL-16 activity, process for preparing the same and their use

ABSTRACT

A nucleic acid which can be used to express a polypeptide with interleukin-16 activity in a prokaryotic or eukaryotic host cell wherein the nucleic acid codes for a polypeptide with the amino acid sequence SEQ ID NO:2 or a SEQ ID NO:2 elongated N-terminally by an aspartic acid residue or a form shortened at the C-terminus by up to 8 amino acids, and is suitable for the production of an active IL-16 polypeptide.

This application is a national stage entry of PCT/EP97/02216 which was filed on Apr. 30, 1997.

The invention concerns polypeptides with IL-16 activity, processes for their production and their use. The invention describes processed IL-16 with high activity.

IL-16 (interleukin-16) is a lymphokine which is also referred to as lymphocyte chemoattracting factor (LCF) or immunodeficiency virus suppressing lymphokine (ISL). IL-16 and its properties are described in WO 94/28134 and WO 96/31607 and by Cruikshank, W. W., et al., Proc. Natl. Acad. Sci. USA 91 (1994) 5109-5113 and by Baier, M., et al., Nature 378 (1995) 563. The recombinant production of IL-16 is also described in these references. According to these IL-16 is a protein with a molecular mass of 13,385 D. Cruikshank also found that ISL elutes in a molecular sieve chromatography as a multimeric form with a molecular weight of 50-60 and 55-60 kD. The chemoattractant activity has been attributed to this multimeric form which is a cationic homotetramer (product information AMS Biotechnology Ltd., Europe, Cat. No. 11177186). A homodimeric form of IL-16 with a molecular weight of 28 kD is described by Baier. However, the chemoattractant activity described by Cruikshank et al. in J. Immunol. 146 (1991) 2928-2934 and the activity of recombinant human IL-16 described by Baier are very small.

The object of the present invention is to improve the activity of IL-16 and to provide IL-16 forms which have a low immunogenicity and are advantageously suitable for a therapeutic application.

The object of the invention is achieved by a nucleic acid which can be used to express a polypeptide with interleukin-16 activity in a prokaryotic or eukaryotic host cell wherein the said nucleic acid

a) corresponds to the DNA sequence of SEQ ID NO:1 or to a DNA elongated at the 5′ end by an aspartic acid codon (GAC), or to its complementary strand

b) hybridizes under stringent conditions with the DNA of SEQ ID NO:1 or with a DNA which is elongated at the 5′ end by an aspartic acid codon,

c) or is a nucleic acid sequence which would hybridize under stringent conditions with the nucleic acid sequences defined by a) or b) without the degeneracy of the genetic code.

d) and at the 5′ end codes for one of the amino acid sequences SEQ ID NO:7 to 10 or for analogous sequences which are elongated N-terminally by one aspartic acid.

Such a nucleic acid preferably codes for a polypeptide with the amino acid sequence SEQ ID NO:2 or for a polypeptide with a sequence which, compared to SEQ ID NO:2, is elongated N-terminally by one aspartic acid codon. In a further preferred embodiment the nucleic acid codes for a polypeptide with IL-16 activity which is shortened by up to 8 amino acids at the C-terminus.

Such a nucleic acid codes for a processed polypeptide with IL-16 activity, particularly preferably natural IL-16 from primates such as human IL-16 or IL-16 of an ape species or of another mammal such as the mouse.

It has surprisingly turned out that FIG. 2 of WO 94/28134 does not describe the correctly processed IL-16. The start codon “ATG” of the precursor form of the protein does not begin with nucleotide 783 but rather with nucleotide 54 or 174. This reading frame results when an A is inserted after nucleotide 156, a C is inserted after nucleotide 398 and a G is inserted after nucleotide 780. The sequence also shows further differences to FIG. 2 of WO 94/28134. These are for example nucleotide substitutions (313 G into A, 717 C into A). IL-16 is processed during the expression in eukaryotic cells. In this way a polypeptide according to SEQ ID NO:2 and/or a polypeptide with a sequence that is elongated N-terminally compared to SEQ ID NO:2 by one aspartic acid codon. Knowledge of the processed IL-16 enables the production of IL-16 and derivatives with high activity and low immunogenicity.

The sequence of IL-16 can differ to a certain extent from protein sequences coded by such DNA sequences. Such sequence variations may be amino acid substitutions, deletions or additions. However, the amino acid sequence of IL-16 is preferably at least 75% and particularly preferably at least 90% identical to the amino acid sequence of SEQ ID NO:2. Variants of parts of the amino and of the nucleic acid sequences SEQ ID NO:1/SEQ ID NO:2 are for example described in WO 96/31607 and the International Patent Applications PCT/EP96/05662 and PCT/EP96/05661. However, it is essential that the polypeptides have a correct N-terminus. Consequently proteins are preferred in which the first three to ten amino acids of the N-terminus are unchanged and thus begin N-terminally with the amino acid sequences SEQ ID NO:6 to 8 or with analogous sequences which are extended N-terminally by an aspartic acid residue. Proteins are also preferred which are shortened at the C-terminus by up to 8 amino acids.

Nucleic acids within the sense of the invention are understood for example as DNA, RNA and nucleic acid derivatives and analogues. Preferred nucleic acid analogues are those compounds in which the sugar phosphate backbone is replaced by other units such as e.g. amino acids. Such compounds are referred to as PNA and are described in WO 92/20702. Since PNA-DNA bonds are for example stronger than DNA-DNA bonds, the stringent conditions described below are not applicable to PNA-DNA hybridization. However, suitable hybridization conditions are described in WO 92/20703.

The term “IL-16” is understood within the sense of the invention as a polypeptide with the activity of IL-16. IL-16 preferably exhibits the stated action in the test procedure described in WO 96/31607 or stimulates cell division according to WO 94/28134.

IL-16 binds to CD4⁺ lymphocytes and can suppress the replication of viruses such as for example HIV-1, HIV-2 and SIV. The function of IL-16 is not limited by its presentation in the MHC complex.

In particular IL-16 exhibits one or several of the following properties:

binding to T cells via the CD4 receptor,

stimulation of the expression of the IL-2 receptor and/or HLA-DR antigen on CD4⁺ lymphocytes,

stimulation of the proliferation of T helper cells in the presence of IL-2,

suppression of the proliferation of T helper cells stimulated with anti-CD3 antibodies,

suppression of the replication of viruses preferably of HIV-1, HIV-2 or SIV.

Nucleic acids are preferred which hybridize with nucleic acids of the sequence SEQ ID NO:1 under stringent conditions. The term “hybridize under stringent conditions” means that two nucleic acid fragments hybridize with one another under standardized hybridization conditions as described for example in Sambrook et al., “Expression of cloned genes in E. coli” in Molecular Cloning: A laboratory manual (1989), Cold Spring Harbor Laboratory Press, New York, USA. Such conditions are for example hybridization in 6.0×SSC at about 45° C. followed by a washing step with 2×SSC at 50° C. In order to select the stringency the salt concentration in the washing step can for example be chosen between 2.0×SSC at 50° C. for low stringency and 0.2×SSC at 50° C. for high stringency. In addition the temperature of the washing step can be varied between room temperature, ca. 22° C., for low stringency and 65° C. for high stringency.

IL-16 is preferably produced recombinantly in prokaryotic or eukaryotic host cells. Such production processes are described for example in WO 94/28134 and WO 96/31607 which are also for this purpose a subject matter of the disclosure of the present invention. However, in order to obtain the forms according to the invention of IL-16 by recombinant production in a defined and reproducible manner, additional measures have to be taken beyond the processes for recombinant production familiar to a person skilled in the art.

Recombinant IL-16 can be produced by methods familiar to a person skilled in the art as heterologous expression or as homologous expression (after homologous recombination of the IL-16 nucleic acid into the genome of the host organism). For this a DNA is firstly produced which is able to produce a protein which has the activity of IL-16. The DNA is cloned into a vector which can be transferred into a host cell and can be replicated there. Such a vector contains regulator elements in addition to the IL-16 sequence which are necessary for the expression of the DNA sequence. This vector which contains the IL-16 sequence and the regulator elements is transferred into a vector which is able to express the DNA of IL-16. The host cell is cultured under conditions which are suitable for the amplification of the vector and IL-16 is isolated. In this process suitable measures ensure that the protein can adopt an active tertiary structure in which it exhibits IL-16 properties.

The nucleic acid sequence of the protein can also be modified. Such modifications are for example:

modification of the nucleic acid in order to introduce various recognition sequences of restriction enzymes to facilitate the steps of ligation, cloning and mutagenesis

modification of the nucleic acid to incorporate preferred codons for the host cell

extension of the nucleic acid by additional operator elements in order to optimize expression in the host cell.

The protein is preferably expressed in microorganisms in particular in prokaryotes and in this case in E. coli. The expression in prokaryotes yields an unglycosylated polypeptide.

The expression vectors must contain a promoter which allows expression of the protein in the host organism. Such promoters are known to a person skilled in the art and are for example the lac promoter (Chang et al., Nature 198 (1977) 1056), trp promoter (Goeddel et al., Nuc. Acids Res. 8 (1980) 4057), λ_(PL) promoter (Shimatake et al., Nature 292 (1981) 128) and T5 promoter (U.S. Pat. No. 4,689,406). Synthetic promoters such as for example the tac promoter (U.S. Pat. No. 4,551,433) are also suitable. Coupled promoter systems are equally suitable such as for example the T7-RNA polymerase/promoter system (Studier et al., J. Mol. Biol. 189 (1986) 113). Hybrid promoters composed of a bacteriophage promoter and the operator region of the microorganism (EP-A 0 267 851) are also suitable. An effective ribosome binding site is necessary in addition to the promoter. In the case of E. coli this ribosome binding site is referred to as the Shine-Dalgarno (SD) sequence (Sambrook et al., “Expression of cloned genes in E. coli” in Molecular Cloning: A laboratory manual (1989) Cold Spring Harbor Laboratory Press, New York, USA).

In order to improve expression it is possible to express the protein as a fusion protein. In this case a DNA sequence which codes for the N-terminal part of an endogenous bacterial protein or another stable protein is usually fused to the 5′ end of the sequence coding for IL-16. Examples of this are for example lacZ (Phillips and Silhavy, Nature 344 (1990) 882-884), trpE (Yansura, Meth. Enzymol. 185 (1990) 161-166).

After expression of the vector which is preferably a biologically functional plasmid or a viral vector, the fusion proteins are preferably cleaved with enzymes (e.g. factor Xa) (Nagai et al., Nature 309 (1984) 810). Further examples of cleavage sites are the IgA protease cleavage site (WO 91/11520, EP-A 0 495 398), the ubiquitin cleavage site (Miller et al., Bio/Technology 7 (1989) 698) and the enterokinase cleavage site.

The proteins expressed in this manner in bacteria are obtained in the usual manner by disrupting the bacteria and isolating the protein.

In a further embodiment it is possible to secrete the proteins from the microorganisms as active proteins. For this a fusion product is preferably used which is composed of the signal sequence that is suitable for secretion of proteins in the host organisms used and of the nucleic acid that codes for the protein. In this case the protein is either secreted into the medium (in gram-positive bacteria) or into the periplasmatic space (in gram-negative bacteria). It is expedient to insert a cleavage site between the signal sequence and the sequence coding for IL-16 which allows cleavage of the protein either during processing or in an additional step. Such signal sequences are derived for example from ompA (Ghrayeb et al., EMBO J. 3 (1984) 2437), phoA (Oka et al., Proc. Natl. Acad. Sci. USA 82 (1985) 7212).

The vectors additionally contain terminators. Terminators are DNA sequences that signal the end of a transcription process. They are usually characterized by two structural features: a reversely repetitive G/C-rich region which can form a double helix intramolecularly as well as a number of U (or T) residues. Examples are the main terminator in the DNA of the phages fd (Beck and Zink, Gene 16 (1981) 35-38) and rrnB (Brosius et al., J. Mol. Biol. 148 (1981) 107-127).

In addition the expression vectors usually contain a selectable marker in order to select transformed cells. Such selectable markers are for example the resistance genes for ampicillin, chloramphenicol, erythromycin, kanamycin, neomycin and tetracyclin (Davies et al., Ann. Rev. Microbiol. 32 (1978) 469). Selectable markers which are equally suitable are the genes for essential substances for the biosynthesis of substances necessary for the cell such as e.g. histidine, tryptophan and leucine.

Numerous suitable bacterial vectors are known. Vectors have for example been described for the following bacteria: Bacillus subtilis (Palva et al., Proc. Natl. Acad. Sci. USA 79 (1982) 5582), E. coli (Aman et al., Gene 40 (1985) 183; Studier et al., J. Mol. Biol. 189 (1986) 113), Streptococcus cremoris (Powell et al., Appl. Environ. Microbiol. 54 (1988) 655), Streptococcus lividans and Streptomyces lividans (U.S. Pat. No. 4,747,056).

Further genetic engineering methods for the production and expression of suitable vectors are described in J. Sambrook et al., Molecular cloning: a laboratory manual (1989), Cold Spring Harbor Laboratory Press, New York, N.Y.

In addition to prokaryotic microorganisms it is also possible to express recombinant IL-16 in eukaryotes (such as for example CHO cells, yeast or insect cells). The yeast system or insect cells are preferred as a eukaryotic expression system. Expression in yeast can be achieved by means of three types of yeast vectors: (integrating YI_(P) (yeast integrating plasmids) vectors, replicating YR_(P) (yeast replicon plasmids) vectors and episomal YE_(P) (yeast episomal plasmids) vectors. More details of this are described for example in S. M. Kingsman et al. Tibtech 5 (1987) 53-57.

The invention in addition concerns a prokaryotic or eukaryotic host cell which is transformed or transfected with a nucleic acid which codes for an IL-16 polypeptide according to the invention in such a way that the host cell expresses the said polypeptide. Such a host cell usually contains a biologically functional nucleic acid vector, preferably a DNA vector, a plasmid DNA, which contains this nucleic acid.

A monomeric IL-16 polypeptide is additionally preferred which cannot be cleaved into further subunits.

It has surprisingly turned out that the nucleic acid and the protein sequence of IL-16 described in WO 94/28134 do not correspond to the natural human sequences. It is merely a non-natural IL-16 analogue. However, a protein is preferably used for a therapeutic application which is either identical to the natural protein or only differs slightly from the natural protein and at least exhibits comparable activity and immunogenicity. The sequence of the protein is described in SEQ ID NO:2 (optionally with N-terminal elongation by an aspartic acid residue and/or shortening at the C-terminus by up to 8 amino acids).

The nucleic acid sequence of IL-16 can, within the scope of the invention contain deletions, mutations and additions. The monomeric form of IL-16 can be multimerized in a preferred embodiment. The activity of IL-16 can be increased in this manner. Such multimeric forms are preferably dimeric, tetrameric or octameric forms.

In a further embodiment the polypeptides of the invention can additionally contain a defined amount of metal ions, the number of metal ions per subunit being preferably 0.5 to 2.

Numerous metal ions are suitable as metal ions within the sense of the invention. It has turned out that alkaline earth metals as well as elements of the side groups are suitable. Alkaline earth metals, cobalt, zinc, selenium, manganese, nickel, copper, iron, magnesium, calcium, molybdenum and silver are particularly suitable. The ions may be monovalent, divalent, trivalent or tetravalent. Divalent ions are particularly preferred. The ions are preferably added as solutions of MgCl₂, CaCl₂, MnCl₂, BaCl₂, LiCl₂, Sr(NO₃)₂, Na₂MoO₄, AgCl₂.

Such multimeric forms and forms of IL-16 containing metal ions are described in the International Patent Application PCT/EP96/05661.

The polypeptide according to the invention can be produced by culturing a prokaryotic or eukaryotic host cell which has been transformed or transfected with a nucleic acid sequence as claimed in claims 1 or 2 under suitable nutrient conditions and optionally isolating the desired polypeptide. If it is intended to produce the polypeptide in vivo in the context of a gene therapy treatment, the polypeptide is of course not isolated from the cell.

A further subject matter of the invention is a pharmaceutical composition which contains a polypeptide according to the invention in an amount and/or specific activity which is sufficient for a therapeutic application as well as optionally a pharmaceutically suitable diluent, adjuvant and/or carrier.

The polypeptides according to the invention are especially suitable for treating pathological states which are caused by viral replication, in particular retroviral replication, and for immunomodulation. Such therapeutic applications are also described in WO 96/31607. This also describes diagnostic test procedures.

The polypeptides according to the invention can also be preferably used for immunosuppression. This immunosuppression is preferably achieved by an inhibition of the helper function of the TH₀ and/or TH₁ and/or TH₂ cells. Hence the polypeptides according to the invention are of therapeutic value in all diseases in which an immunodysregulatory component is postulated in the pathogenesis and in particular a hyperimmunity. Diseases which can be treated by IL-16 in cardiology/angiology are for example diseases such as myocarditis, endocarditis and pericarditis, in pulmonology for example bronchitis, asthma, in haematology autoimmune neuropenias and transplant rejection, in gastroenterology chronic gastritis, in endocrinology diabetes mellitus type I, in nephrology glomerulonephritis, rheumatic diseases, diseases in ophthalmology, in neurology such as multiple sclerosis and eczemas in dermatology. The polypeptides according to the invention can be used in particular for autoimmune diseases, allergies and to avoid transplant rejections.

The invention furthermore concerns the use of the nucleic acids according to the invention within the context of gene therapy. Retroviral or non-viral vector systems are for example suitable vector systems for this.

In addition the invention concerns a polyclonal or monoclonal anti-IL-16 antibody or an immunoactive fragment thereof which binds to the first 3-20 amino acids of SEQ ID NO:2 or to SEQ ID NO:2 elongated N-terminally by an aspartic acid residue as well as processes for the production of such antibodies and their use for the determination of IL-16 and for determining viral infections in eukaryotic cells and in particular in mammalian cell material. Virus-activated mammalian cells and in particular T cells can also be determined with IL-16. The production of such antibodies is carried out by immunization with a polypeptide according to the invention. The production of such an antibody is carried out according to processes familiar to a person skilled in the art by immunizing with an immunogen which contains the first 3-20 amino acids of SEQ ID NO:2 or a SEQ ID NO:2 elongated N-terminally by an aspartic acid residue as the hapten. Subsequently the antibody can be isolated in the usual manner from the immunized mammal and optionally a monoclonal antibody can be produced.

The following examples and publications as well as the sequence protocol further elucidate the invention the protective scope of which results from the patent claims. The processes described are to be understood as examples that still describe the object of the invention even after modifications.

EXAMPLE 1 Cloning, Expression and Purification of IL-16

1.1 RNA Isolation

5×10⁷ PBMC (from humans or monkeys) were cultured for 48 hours with 10 μg/ml concanavalin A and 180 U/ml IL-2. In order to prepare the RNA, the cells were washed once with PBS and subsequently lysed with 5 ml denaturation solution (RNA isolation kit, Stratagene). The lysate was kept on ice for 15 min after addition of 1 ml Na acetate, 5 ml phenol and 1 ml chloroform/isoamyl alcohol (24:1). The aqueous phase was subsequently mixed with 6 ml isopropanol in order to precipitate the RNA and stored for 2 hours at −20° C. The precipitate was finally washed once with pure ethanol and dissolved in 150 μl H₂O. The yield was determined photometrically and was 120 μg.

1.2 CDNA Synthesis

The mixture for the cDNA synthesis contained 10 μg RNA, 0.2 μg oligo-dT, 13 mM DTT and 5 μl bulk first strand reaction mix (first strand CDNA synthesis kit, Pharmacia) in an amount of 15 μl. The mixture was incubated for 1 hour at 37° C. and subsequently stored at −20° C. for later use.

The amplification, cloning of IL-16 cDNA and production of an expression clone is carried out as described in Wo 94/28134 or WO 96/31607 taking the modified sequences into consideration.

1.3 10 l Fermentation of an E. coli Expression Clone for IL-16 and High Pressure Disruption

Precultures are set up from stock cultures (plate smear or ampoules stored at −20° C.) which are incubated at 37° C. while shaking. The inoculation volume into the next higher dimension is 1-10 vol. % in each case. Ampicillin (50-100 mg/l) is used in the preculture and main culture to select against plasmid loss.

Enzymatically digested protein and/or yeast extract as a N- and C-source as well as glycerol and/or glucose as an additional C-source are used as nutrients. The medium is buffered to pH 7 and metal salts are added at physiologically tolerated concentrations to stabilize the fermentation process. The fermentation is carried out as a feed batch with a mixed yeast extract/C sources dosage. The fermentation temperature is 25-37° C. The dissolved partial oxygen pressure (pO₂) is kept about below 20% by means of the aeration rate, r.p.m. regulation and dosage rate. The growth is determined by determining the optical density (OD) at 528 nm. The expression of IL-16 is induced by means of IPTG. After a fermentation period of 10 to 20 hours the biomass is harvested by centrifugation at OD standstill.

The biomass is taken up in 50 mM sodium phosphate, 5 mM EDTA, 100 mM sodium chloride, pH 7 and is disrupted at 1000 bar by means of a continuous high pressure press. The suspension obtained in this manner is centrifuged again and the supernatant which contains the dissolved IL-16 is processed further.

1.4 Purification of Recombinant Human IL-16

550 ml lysis supernatant in 50 mM sodium phosphate, 5 mM EDTA, 100 mM NaCl, pH 7.2 was admixed with 55 ml 5 M NaCl, 60 mM MgCl₂, pH 8.0, stirred for 30 minutes and subsequently centrifuged for 30 minutes at 20,000 g. 400 ml of the supernatant was taken up on a nickel-chelate Sepharose column (V=60 ml; Pharmacia), which had previously been loaded with 30 μMol NiCl₂/ml gel and equilibrated with 50 mM sodium phosphate, 0.2 M NaCl, pH 8.0. The column was subsequently washed with 300 ml 50 mM sodium phosphate, 0.5 M NaCl, pH 7.0 and the IL-16 fusion protein was then eluted with a gradient of 0 M to 300 mM imidazole, pH 7.0 in 50 mM sodium phosphate, 0.1 M NaCl, pH 7.0 (2×0.5 l gradient volumes). Fractions containing IL-16 were identified by means of SDS-PAGE, pooled and dialysed against 20 mM sodium phosphate, pH 7.0.

300 mg of the fusion protein obtained in this way was dialysed at 4° C. against 20 l 20 mM imidazole, pH 5.5 and subsequently centrifuged for 30 minutes at 20,000 g in order to remove turbidities. The supernatant of the centrifugation was subsequently adjusted to pH 8.5 with NaOH, admixed with 0.3 mg thrombin (Boehringer Mannheim GmbH) and incubated for 4 hours at 37° C. Subsequently the cleavage mixture was adjusted to pH 6.5 with HCl and the conductivity was set to 1.7 mS by dilution with H₂O. The sample was applied to a Q-Sepharose FF column (45 ml; Pharmacia) which had previously been equilibrated with 20 mM imidazole, pH 6.5. IL-16 was eluted using a gradient of 0 to 0.3 M NaCl in 20 mM imidazole, pH 6.5. Fractions containing IL-16 were identified by means of SDS-PAGE and pooled. The identity of IL-16 was confirmed by means of mass analysis (molecular weight 13,566±3D) and automated N-terminal sequence analysis. The UV absorbance of IL-16 at 280 nm and a calculated molar extinction coefficient of 5540 M⁻¹ cm⁻¹ at this wavelength (Mack et al. (1992) Analyt. Biochem. 200, 74-80) were used to determine the concentration.

In order to obtain the desired N-terminus it is optionally re-cleaved with an amino peptidase (e.g. α aminoacyl peptide hydrolase) or dipeptidyl peptidase (e.g. cathepsin CCATH).

The IL-16 obtained in this manner had a purity of more than 95% in SDS-PAGE under reducing conditions.

A Vydac, Protein & Peptide C18, 4×180 mm column was used to analyse purity by means of RP-HPLC. It was eluted with a linear gradient of 0% to 80% B (solvent B: 90% acetonitrile in 0.1% TFA; solvent A: 0.1% TFA in H₂O) within 30 minutes at a flow rate of 1 ml/min. Detection was at 220 nm.

EXAMPLE 2 Production of Shortened IL-16 using an Enterokinase Cleavage Site

2.1 Expression clone

The amplification and cloning of IL-16 CDNA and the preparation of an expression clone are carried out as described in WO 94/28134 or WO 96/31607 taking into account the modified sequences.

An oligonucleotide having the sequence SEQ ID NO:3 is used as a forwards primer which contains an EcoRI site, 6 His and an enterokinase cleavage site (D₄K):

cccgaattc tatg cat cac cac cac cac cac gatgacgacgacaaa-tctgcagcctcagcctctgc    EcoRI                   H6                    D₄K

An oligonucleotide having the sequence SEQ ID NO:6 which also contains an EcoRI site, 6 His and an Enterokinase cleavage site (D₄K) is used as a forwards primer for the sequence elongated at the 5′ end by one aspartic acid codon:

cccgaattc tatg cat cac cac cac cac cac gatgacgacgacaaa-gactctgcagcctcagcctc    EcoRI                   H6                     D₄K

Either oligonucleotide IL-16-R₁ (SEQ ID NO:4): IL-16-R₁: gcg gat cca agc tta gga gtc tcc agc agc tgt g

or oligonucleotide IL-16-R₂ (SEQ ID NO:5) are used as the reverse primers:

IL-16-R₂: gcq gat cca agc tta ttc ctt gga ctg gag gct ttt tc

The two reverse primers contain BamHI and HindIII cleavage sites for cloning.

A sequence is obtained with IL-16-R₁ which codes for a protein according to SEQ ID NO:2.

A sequence is obtained with IL-16-R2 which codes for an IL-16 shortened by 8 amino acids at the C-terminus. This C-terminal IL-16 is also active.

The PCR reaction, cloning and preparation of the expression clone (fusion protein with an N-terminal poly-His part for purification) are carried out according to standard conditions:

0.2 mM dNTP mix, 1 pmol/μl each of forward and reverse primer, 1×high fidelity buffer (Boehringer Mannheim, D), 1.5 mM MgCl₂, 2.6 U high fidelity enzyme mix (Boehringer Mannheim, D).

20 μl final volume instrument: Perkin Elmer GeneAmp 9600

Reaction course:

3 min 94° C., 1 min 56° C., 2 min 72° C., then 25 cycles (20 sec 94° C., 20 sec 56° C., 1 min 72° C.).

2.2 Fermentation

The fermentation is carried out analogously to example 1.3.

2.3 Purification and Cleavage

700 ml lysis supernatant in 50 mM sodium phosphate, 5 mM EDTA, 100 mM NaCl, pH 7.2 was admixed with 70 ml 5 M NaCl, 60 MM MgCl₂, pH 8.0, stirred for 30 min and subsequently centrifuged for 30 min at 20,000 g. The centrifuged supernatant was applied to a nickel-chelate column (v=200 ml, Pharmacia) which had previously been loaded with a NiSO₄ solution (c=10 mg/ml) and equilibrated with 50 mM sodium phosphate, 0.5 M NaCl, pH 8.0. The column was subsequently washed with equilibration buffer until the base line (UV detection at 280 nm) was almost reached. Afterwards the column was rinsed with 1 l 50 mM sodium phosphate, 0.5 M NaCl, pH 7.0 and with 1 l 50 mM sodium phosphate, 0.1 M NaCl, pH 7.0. The fusion protein was eluted with a gradient of 0-300 mM imidazole, pH 7.0 in 50 mM sodium phosphate, 0.1 M NaCl, pH 7.0 (2×1.6 l). Fractions containing IL-16 were identified by means of SDS-PAGE and pooled. This IL-16 pool was concentrated in a Provario (Filtron, membrane omega 5 K) to a concentration of 5 mg protein/ml and dialysed against 50 mM Tris, pH 8.0.

An equivalent of the pool containing 100 mg fusion protein was diluted with 50 mM Tris, pH 8.0 to a protein concentration of c=1 mg/ml for the enterokinase cleavage. After addition of 33 μg enterokinase (Boehringer Mannheim; 1:3000 w/w) the cleavage mixture was incubated overnight (14 h) at 37° C. Subsequently the pH value was adjusted to pH 6.5 with HCl.

Uncleaved IL-16 was removed by stirring in 20 ml nickel-chelate sepharose (for preparation see above; binding time 2 h) and subsequent centrifugation (10,000 g) or by suction filtration of the supernatant over a filter frit. The identity of the cleaved IL-16 contained in the supernatant was confirmed by N-terminal sequencing and mass analysis. The purity was checked by SDS-PAGE and RP-HPLC (Vydac, diphenyl, 4.6×150 mm, linear gradient of 20% to 95% B in 45 minutes; solution A: 20 mM potassium phosphate in H₂O, pH 7.5; solution B: 100% acetonitrile.

EXAMPLE 3 Cleavage of Recombinant IL-16 with Cell Lysate

3.1 Separation of CD8⁺ and CD4⁺ lymphocytes via MACS

The lymphocytes isolated from a buffy coat by means of Ficoll gradients are resuspended in 500 μl PBS-azide/1×10⁸ cells (phosphate buffered saline without Ca²⁺ and Mg²⁺, 0.01% sodium azide, 5 mM EDTA, pH 7.2). After addition of 20 ml CD8 microbeads/1×10⁷ cells to be expected (mouse anti-human CD8 antibodies, conjugated with magnetic particles, Miltenyi Biotec GmbH), they are incubated for 15 min at 4° C. 2 mg DTAF/1×10⁷ expected cells (anti-mouse IgG FITC conjugated, Dianova Company) is added for a further 5 min at 4° C. After dilution with 25 ml PBS-azide/1% BSA it is again centrifuged (10 min, 1200 rpm, 4° C.). The supernatant is discarded, the cells are resuspended in 2 ml PBS/1% BSA and the cell suspension is applied to a column which is located in a magnetic separator (Miltenyi Biotec GmbH). The CD8⁺ cells to which the CD8 microbeads are coupled are retained in the column, thus the flow fraction contains all lymphocytes (ca. 80% CD4⁺ cells) except the CD8⁺ cells. After washing the column is taken out of the holder and the CD8⁺ cell fraction is eluted with PBS-azide/1% BSA. The flow fraction and the CD8⁺ cell fraction are centrifuged, resuspended in cell culture medium (RPMI 1640, 20% FCS, 2 mM glutamine, 180 U/ml IL-2), the cell count is adjusted to 3×10⁶ cells/ml and the cells are stimulated with PHA (9 mg/ml). The quality of the separation of the lymphocyte subpopulation is checked by means of FACS.

3.2 Preparation of Cell Lysate and Digestion of IL-16

1×10⁸ CD8⁺ lymphocytes which had been stimulated for three days with PHA are lysed for 10 min on ice in 2 ml PBS which is admixed with 1% Triton X100. Then cell debris and cell nuclei are removed by centrifugation. 45 μl of the cell lysate obtained in this manner is incubated for 16 hours at room temperature with 10 μg recombinant IL-16 which was expressed either at the amino-terminal or carboxy-terminal end in fusion with a histidine tag (HIS tag, e.g. six histidine with cleavage site cf. WO 94/28134). Then fragments carrying the HIS tag are purified with the aid of a nickel agarose matrix. After further purification of the fragments that are formed in HPLC, the masses of the fragments are determined by mass spectrography and hence the size of the N-terminal fragment is determined. In this manner a naturally processed IL-16 fragment was identified which starts with the N-terminus described in SEQ ID NO:1/2 or with an N-terminus elongated by an aspartic acid codon.

List of References

Aman et al., Gene 40 (1985) 183

Baier, M., et al., Nature 378 (1995) 563

Beck and Zink, Gene 16 (1981) 35-58

Brosius et al., J. Mol. Biol. 148 (1981) 107-127

Chang et al., Nature 198 (1977) 1056

Cruikshank, W. W., et al., J. Immunol. 146 (1991) 2928-2934

Cruikshank, W. W., et al., Proc. Natl. Acad. Sci. USA 91 (1994) 5109-5113

Davies et al., Ann. Rev. Microbiol. 32 (1978) 469

EP-A 0 267 851

EP-A 0 495 398

European Patent Application No. 95 113 013.7

Ghrayeb et al., EMBO J. 3 (1984) 2437

Goeddel et al., Nuc. Acids Res. 8 (1980) 4057

International Patent Application PCT/EP96/05661

International Patent Application PCT/EP96/05662

Kingsman, S. M., et al, Tibtech 5 (1987) 53-57

Mack et al., Analyt. Biochem. 200 (1992) 74-80

Miller et al., Bio/Technology 7 (1989) 698

Nagai et al., Nature 309 (1984) 810

Oka et al., Proc. Natl. Acad. Sci. USA 82 (1985) 7212

Palva et al., Proc. Natl. Acad. Sci. USA 79 (1982) 5582

Phillips and Silhavy, Nature 344 (1990) 882-884

Powell et al., Appl. Environ. Microbiol. 54 (1988) 655

Sambrook et al., “Expression of cloned genes in E. coli” in Molecular Cloning: A laboratory manual (1989), Cold Spring Harbor Laboratory Press, New York, USA

Shimatake et al., Nature 292 (1981) 128

Studier et al., J. Mol. Biol. 189 (1986) 113

U.S. Pat. No. 4,551,433

U.S. Pat. No. 4,689,406

U.S. Pat. No. 4,747,056

WO 91/11520

WO 92/20702

WO 92/20703

WO 94/28134

WO 96/31607

Yansura, Meth. Enzymol. 185 (1990) 161-166

10 366 base pairs nucleic acid double linear cDNA CDS 1..366 1 TCT GCA GCC TCA GCC TCT GCA GCC AGT GAT GTT TCT GTA GAA TCT ACA 48 Ser Ala Ala Ser Ala Ser Ala Ala Ser Asp Val Ser Val Glu Ser Thr 1 5 10 15 GCA GAG GCC ACA GTC TGC ACG GTG ACA CTG GAG AAG ATG TCG GCA GGG 96 Ala Glu Ala Thr Val Cys Thr Val Thr Leu Glu Lys Met Ser Ala Gly 20 25 30 CTG GGC TTC AGC CTG GAA GGA GGG AAG GGC TCC CTA CAC GGA GAC AAG 144 Leu Gly Phe Ser Leu Glu Gly Gly Lys Gly Ser Leu His Gly Asp Lys 35 40 45 CCT CTC ACC ATT AAC AGG ATT TTC AAA GGA GCA GCC TCA GAA CAA AGT 192 Pro Leu Thr Ile Asn Arg Ile Phe Lys Gly Ala Ala Ser Glu Gln Ser 50 55 60 GAG ACA GTC CAG CCT GGA GAT GAA ATC TTG CAG CTG GGT GGC ACT GCC 240 Glu Thr Val Gln Pro Gly Asp Glu Ile Leu Gln Leu Gly Gly Thr Ala 65 70 75 80 ATG CAG GGC CTC ACA CGG TTT GAA GCC TGG AAC ATC ATC AAG GCA CTG 288 Met Gln Gly Leu Thr Arg Phe Glu Ala Trp Asn Ile Ile Lys Ala Leu 85 90 95 CCT GAT GGA CCT GTC ACG ATT GTC ATC AGG AGA AAA AGC CTC CAG TCC 336 Pro Asp Gly Pro Val Thr Ile Val Ile Arg Arg Lys Ser Leu Gln Ser 100 105 110 AAG GAA ACC ACA GCT GCT GGA GAC TCC TAG 366 Lys Glu Thr Thr Ala Ala Gly Asp Ser * 115 120 121 amino acids amino acid linear protein 2 Ser Ala Ala Ser Ala Ser Ala Ala Ser Asp Val Ser Val Glu Ser Thr 1 5 10 15 Ala Glu Ala Thr Val Cys Thr Val Thr Leu Glu Lys Met Ser Ala Gly 20 25 30 Leu Gly Phe Ser Leu Glu Gly Gly Lys Gly Ser Leu His Gly Asp Lys 35 40 45 Pro Leu Thr Ile Asn Arg Ile Phe Lys Gly Ala Ala Ser Glu Gln Ser 50 55 60 Glu Thr Val Gln Pro Gly Asp Glu Ile Leu Gln Leu Gly Gly Thr Ala 65 70 75 80 Met Gln Gly Leu Thr Arg Phe Glu Ala Trp Asn Ile Ile Lys Ala Leu 85 90 95 Pro Asp Gly Pro Val Thr Ile Val Ile Arg Arg Lys Ser Leu Gln Ser 100 105 110 Lys Glu Thr Thr Ala Ala Gly Asp Ser 115 120 66 base pairs nucleic acid single linear other nucleic acid /desc = “forward primer” 3 CCCGAATTCT ATGCATCACC ACCACCACCA CGATGACGAC GACAAATCTG CAGCCTCAGC 60 CTCTGC 66 34 base pairs nucleic acid single linear other nucleic acid /desc = “reverse primer IL-16-R1” 4 GCGGATCCAA GCTTAGGAGT CTCCAGCAGC TGTG 34 38 base pairs nucleic acid single linear other nucleic acid /desc = “reverse primer IL-16-R2” 5 GCGGATCCAA GCTTATTCCT TGGACTGGAG GCTTTTTC 38 66 base pairs nucleic acid single linear other nucleic acid /desc = “forward primer” 6 CCCGAATTCT ATGCATCACC ACCACCACCA CGATGACGAC GACAAAGACT CTGCAGCCTC 60 AGCCTC 66 7 amino acids amino acid single linear peptide 7 Ser Ala Ala Ser Ala Ser Ala 1 5 6 amino acids amino acid single linear peptide 8 Ser Ala Ala Ser Ala Ser 1 5 5 amino acids amino acid single linear peptide 9 Ser Ala Ala Ser Ala 1 5 4 amino acids amino acid single linear peptide 10 Ser Ala Ala Ser 1 

What is claimed is:
 1. An isolated nucleic acid encoding a polypeptide with interleukin-16 (IL-16) activity, wherein the IL-16 activity is at least one activity selected from the group consisting of (1) binding to T cells via the CD4 receptor, (2) stimulating the expression of the IL-2 receptor and/or HLA-DR antigen on CD4* lymphocytes, (3) stimulating the proliferation of T helper cells in the presence of IL-2, (4) suppressing the proliferation of T helper cells stimulated with anti-CD3 antibodies, and (5) suppressing the replication of viruses, wherein the nucleic acid sequence is selected from the group consisting of (A) the nucleic acid sequence of SEQ ID NO:1, (B) the nucleic acid sequence if SEQ ID NO:1 extended at the 5′-end by an aspartic acid codon, and (C) the nucleic acid sequence of SEQ ID NO:1 shortened at the 3′-end by 1 to 8 amino acid codons.
 2. A host cell which is transformed or transfected with a nucleic acid according to claim 1, wherein the host cell expresses the polypeptide with IL-16 activity.
 3. The host cell of claim 2, wherein the host cell is a prokaryotic cell.
 4. The host cell of claim 2, wherein the host cell is a eukaryotic cell.
 5. A vector containing a nucleic acid according to claim
 1. 6. A polypeptide with IL-16 activity which is encoded by a nucleic acid according to claim
 1. 7. A multimeric polypeptide with IL-16 activity, wherein the multimeric polypeptide is composed of a plurality of subunits, and wherein the subunits comprise a polypeptide according to claim
 6. 8. The multimeric polypeptide of claim 7, wherein the multimeric polypeptide is composed of 4 to 32 subunits.
 9. The multimeric polypeptide of claim 7, wherein the multimeric polypeptide further comprises 0.5 to 2 metal ions per subunit.
 10. The multimeric polypeptide of claim 9, wherein the metal ions are selected from the group consisting of alkaline earth metal, cobalt, zinc, selenium, manganese, nickel, copper, iron, molybdenum and silver ions.
 11. A process for producing a polypeptide with IL-16 activity, comprising (a) transforming or transfecting a host cell with a nucleic acid according to claim 1, to obtain a transformed or transfected host cell; and (b) expressing the polypeptide in the transformed or transfected host cell.
 12. The process of claim 11, further comprising isolating the polypeptide.
 13. The process of claim 11, wherein the polypeptide is expressed as a fusion protein comprising a protein endogenous to the host cell fused to the polypeptide with IL-16 activity.
 14. The process of claim 11, further comprising fusing a signal sequence to the nucleic acid such that the polypeptide is secreted as an active protein.
 15. The process of claim 11, wherein the host cell is a prokaryotic cell.
 16. The process of claim 11, wherein the host cell is a eukaryotic cell.
 17. A pharmaceutical composition comprising a polypeptide according to claim 6, in combination with a pharmaceutically acceptable carrier.
 18. A complementary nucleic acid to the isolated nucleic acid of claim
 1. 